bug: Fix missing exception

Author: tony

src/tmuxp/workspace/builder.py

@@ -156,7 +156,7 @@ def __init__(self, sconf, plugins=[], server=None):
         """
 
         if not sconf:
-            raise exc.EmptyConfigException("session configuration is empty.")
+            raise exc.EmptyWorkspaceException("session configuration is empty.")
 
         # validation.validate_schema(sconf)